This invention relates to a foundation assembly for wooden buildings to be protected against possible damage from white ants and a method for forming the building foundation assembly.
At present, it has been known that about 50-60% of existing wooden buildings are damaged by white ants and the number of wooden buildings suffering from white ant damage will increase year after year.
Since the conventional foundation assemblies for wooden buildings are so constructed that white ants are willing to inhabit the buildings, the wooden buildings are easily damaged by white ants. Any of the conventional building foundation assemblies comprises a concrete foundation and a wooden sill built on the concrete foundation. The concrete foundation is generally so formed that the under-floor space is isolated from the air from the atmosphere and the concrete foundation is provided with only a few, if any, ventilation areas. The concrete foundation has a high moisture absorption (after solidification, concrete includes voids which account for about 10% of the total volume of the concrete and provides moisture absorptivity to the concrete foundation) and the wooden sill absorbs moisture from the concrete foundation. White ants are willing to inhabit dark areas where high temperature and moisture conditions are present and the air is stagnant. Thus, in the conventional wooden buildings as described hereinabove, the foundation assembly and the space under the flooring of a wooden building are suitable habitats for white ants. Since white ants are fond of eating substances containing moisture as their provisions, the ants tend to eat away the wooden sill and concrete foundation resulting in the collapse of the building foundation assembly.
Furthermore, the conventional wooden building foundation assembly has the disadvantages that the foundation assembly tends to decay easily and the decay progresses rapidly in the foundation assembly. More particularly, the wooden sill tends to absorb moisture from the concrete foundation and the moisture causes dry rot on the wooden sill, since the under-floor space surrounded by the foundation assembly has poor ventilation and high humidity the dry rot of the wooden will is accelerated. The dry rot on the wood of the wooden sill deteriorates the ferrous material of the concrete foundation which presents a serious problem in the building. In fact, it has been found that in wooden buildings, the dry rot on the connection between the upper surface of the concrete foundation and the lower surface of the wooden sill built on the concrete foundation would spread over the area as much as about one fourth to one third of the entire surface area on the connection in about 20-30 years. In order to solve the dry rot problem, it has been proposed to destroy white ants and/or prevent the ants from inhibiting the wooden building by spraying and/or injecting chemicals such as insecticides for white ants or the like. However, such chemicals tend to deteriorate and cannot be expected to maintain their effectiveness for a long period of time. Thus, the conventional wooden building foundation assembly would again become habitats suitable for white ants after the deteriorate of such chemicals.